Which of the following is a fat-soluble vitamin?

Vitamin D is classified as a fat-soluble vitamin, which means it is soluble in fats and oils, allowing it to be stored in the body's fatty tissues and liver. Fat-soluble vitamins, including A, D, E, and K, can be retained in the body for longer periods, as they do not need to be consumed as frequently as water-soluble vitamins.

In contrast, the other vitamins mentioned, such as Vitamin C and the B vitamins (B12 and B6), are water-soluble. Water-soluble vitamins dissolve in water and are generally not stored in the body to a significant extent. They are excreted through urine, requiring more consistent intake from dietary sources. This fundamental difference in solubility defines how these vitamins are absorbed, utilized, and stored within the body.